Modern refrigeration technology has developed dramatically in the last century. At first, a traditional refrigerating system usually adopted an open-type refrigerating compressor, wherein the compressor and the power part (motor) are separated. In such a configuration, one end of the crankshaft is exposed outside of the compressor, and is connected to the motor through a coupling. The exposed portion of the crankshaft is provided with a shaft-sealing unit for preventing the refrigerant from leaking out.
The motor shell of the closed-type compressor and the compressor body are cast in one body and share an inner chamber. Thus, it's unnecessary to use a shaft-sealing unit so that the leakage problem can be solved. Furthermore, the motor winding can be cooled by utilizing the sucked low-pressure low-temperature refrigerant vapor, thereby greatly improving the cooling condition of the motor.
Today, closed-type compressors are widely applied to refrigerating equipment and air conditioners. As the motor and the closed-type compressor both work in the same sealed environment, the refrigerant must be in contact with the motor (namely, the working medium is not the air in common motors but the refrigerant). Thus, the motor must withstand the influence of the working medium therein.
In the prior art, the most commonly-used refrigerant adopted in closed-type compressors is Freon. However, Freon is environmentally harmful. Therefore, compared with other refrigerants, ammonia is an ideal refrigerant that possesses a higher refrigerating efficiency and is eco-friendly.
Basically, all the electrical materials (insulating materials and conductive materials) used in the Freon-resistant motor insulation system/structure are not ammonia-resistant. Additionally, Freon is a halo-hydrocarbon and has a high insulating performance. Thus, a small amount of moisture existing in the refrigerating system cannot affect the motor. However, when ammonia meets the moisture, an ionic-type conductive substance can be formed. Therefore, it's urgent for those skilled in the art to develop an ammonia-resistant motor capable of reliably working in the closed-type ammonia refrigerating compressor.